Field of the Invention
The present invention relates to an image reading apparatus such as a copying machine and a scanner, in which a sheet feeding portion can be opened and closed with respect to an image reading potion via a connection portion for rotation, and an image forming apparatus.
Description of the Related Art
Conventionally, a fixed reading system and a flow reading system are used in order to optically read an image of a sheet-like original. In the fixed reading system, an image is read while an image reading portion scans an original placed on platen glass having an area larger than the size of the original. On the other hand, in the flow reading system, originals are conveyed one by one from the original feeding portion which is disposed above the image reading portion and images of the originals are read while the originals are being conveyed.
In an image reading apparatus adopting the flow reading system, it is common that the fixed reading system can be also performed by rotatably attaching the original feeding portion to the image reading portion and the original feeding portion can be opened above the platen glass. The image reading apparatus which can perform both of the flow reading system and the fixed reading system is becoming mainstream in copying machines and scanners because a thick original such as a book can be read in addition to the fact that a large number of originals can be read successively.
The attachment of the original feeding portion to the image reading portion is performed by providing a hinge at the back side of the original feeding portion and by fixing the hinge to the back side of the image reading portion. The means of fixing includes two types in general. One type is for fixing the hinge to the image reading apparatus with screws. The other type is for inserting a shaft like hinge into a hole provided at the image reading portion. The former type is mainly used for the case in which strong fixation is necessary in the apparatus which has a large-sized original feeding portion and in which a strong load force is applied to the hinge. On the other hand, the latter type is mainly used for the case in which the apparatus has a small-sized original feeding portion and easy attachment is given high priority.
The most common method of attaching the hinge to the original feeding portion is fastening with screws the hinge to screw holes formed at a frame of the original feeding portion. With this method, the hinge can be maintained by a simple configuration without a special extra member.
The weight of the original feeding portion is about 7 to 23 kg although the weight varies depending on the product specification. Thus, when the configuration is adopted in which screws are simply used for fastening, there is a concern of fastening failure due to damage of the screw holes because the majority of the weight load is applied to the screw holes not only when the original feeding portion is opened but also when the original feeding portion is closed.
As a configuration of fixing a member with screws, Japanese Patent Application Publication 2003-343522 discloses a fixing configuration in which a part of a detachable second member is overlapped with a first member and the overlapped portion is fastened with screws. This configuration could be applied for attaching the hinge to the original feeding portion.
For example, the hinge is formed of a sheet metal as the first member and the original feeding portion is attached to the hinge by nipping a frame of the original feeding portion between the hinge and the second member and by fastening these members by screws. In this case, it is not necessary to provide a screw portion on the frame of the original feeding portion if enough fastening strength between the first member and the second member is obtained. The weight of the original feeding portion is received at the surfaces of the first member and the second member, thereby obtaining stable fixing strength.
Even if the fastening portion between the two members is broken, only the first member or the second member should be replaced with a new one and the original feeding portion itself can be used as it is.
However, in the configuration in which the hinge is attached by nipping the original feeding portion with the first member which is a part of the hinge and the second member, the first member and second member are not fixed to the frame of the original feeding portion until the first member and the second member are fastened to each other. Thus, for example it is necessary to fasten the first member and the second member with the screws by one hand while holding the first member and the second member by another hand, causing difficulty in attachment if the first member is a heavy member such as a hinge.
In exchanging the hinge when an abrupt malfunction occurs to the hinge, the second member does not remain at the predetermined position of the frame and the second member is detached and there is a possibility that the second member gets deep into the apparatus, causing difficulty in detachment of the hinge.